1、Designation: F 1851 98 (Reapproved 2003)Standard Practice forBar Code Verification1This standard is issued under the fixed designation F 1851; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in p
2、arentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes a specific procedure for using abar code verifier to measure and quantify the optical andsymbology characteristics relati
3、ve to the print quality of a barcode symbol and its performance within a bar code readingsystem. Measurements taken with bar code verifiers shouldconform to ANSI ANS X3.1821995 R methodology. Vari-ous printing methods including direct thermal, thermal transfer,electrophotographic, dot matrix, and in
4、k jet methods are usedto produce bar code symbols. Use of this procedure will helpassure repeatability of measurements between operators andpieces of equipment and traceability of those measurements.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its
5、use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:F 1294 Terminology Relating to Automatic IdentificationHard Copy Printing
6、Systems22.2 ANSI Standard:ANSI ANS X3.1821995 R Bar Code Print QualityGuideline32.3 AIM Standard:AIM USA Laymans Guide to ANSI Print Quality42.4 Military Standard:MIL-STD 105E Sampling Procedures and Tables for In-spection by Attributes53. Summary of Practice3.1 Printed bar codes can be analyzed wit
7、h commerciallyavailable bar code verifiers to generate measurement valuesrelative to print quality. Verifiers can have various optical inputdevices and operate in varied spectral ranges with apertures ofdiffering sizes. The validity of the results of verification can beaffected greatly by the select
8、ion of the equipment, spectralresponse and aperture size, as well as the operators use of theequipment. Reporting structure of the test results (symbolgrade) only has meaning when the measuring aperture numberand nominal wavelength also are specified. The methodologycontained within this test method
9、 offers both a standard seriesof procedures for equipment set-up and use, and generalrecommendations, guidelines and information on bar codeverification.4. Significance and Use4.1 This test method provides a way to measure andquantify bar code print quality using commercially availablebar code verif
10、iers. Possible uses include the following.4.1.1 Performance comparisons between media supplied bydifferent manufacturers.4.1.2 Performance comparisons between imaging materialssupplied by different manufacturers.4.1.3 Performance comparisons between printers suppliedby different manufacturers.4.1.4
11、Performance comparisons between different printingmethods.4.1.5 Research and development evaluation of developmen-tal coatings, ribbons and media for various printing methodsfor bar code imaging.4.1.6 Manufacturing process control can use this testmethod to audit product performance.5. Interferences
12、5.1 To avoid interference from external causes, no lami-nates, overcoats or protective materials should be used on orover the samples. These may cause verification results that arenot characteristic of the process being tested.5.2 The equipment selected should be set-up, programmed(if necessary) and
13、 calibrated to the manufacturers recommen-dations.NOTE 1This is extremely important as improper use of verificationequipment through incorrect set-up or calibration, or both, can causemisleading results.1This practice is under the jurisdiction of ASTM Committee F05 on BusinessImaging Products and is
14、 the direct responsibility of Subcommittee F05.03 onResearch.Current edition approved Feb. 10, 1998. Published October 1998.2Annual Book of ASTM Standards, Vol 15.09.3Available from the American National Standards Institute, 25 W. 43rd St., 4thFloor, New York, NY 10036.4Available from AIM USA, 634 A
15、lpha Dr., Pittsburgh, PA 15238.5Available from Standardization Documents Order Desk, Bldg. 4D, 700 RobbinsAve., Philadelphia, PA 19111-5094.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 To avoid interference caused by operating
16、 power volt-age fluctuations, the equipment used should be operated usingthe power source recommended by and in the manner recom-mended by the manufacturer. In the event results can vary withvariation in supply power, such as if the unit operates solelyfrom batteries, it should be determined what re
17、sults variationscan be expected, based upon the manufacturers recommenda-tions, and appropriate compensation should be made.6. Procedure6.1 Calibration/Traceability:6.1.1 Proper calibration is an essential aspect of the opera-tion of a bar code verifier. It is imperative that the operatorproperly an
18、d carefully follow the manufacturers proceduresfor calibration of the verifier. Frequency of calibration shouldbe recommended by the manufacturer, and calibration at afrequency greater than recommended may ensure higher accu-racy and repeatability.6.1.2 To assist in determining if a verifier is bein
19、g operatedwithin the ANSI ANS X3.1821995 R, bar code calibrationor correlation standards are available.66.2 Test Materials:6.2.1 Test specimens should be characteristic or representa-tive of output from a specific process. Appropriate bar codesymbols should be imaged on the media to be tested.6.2.2
20、Test specimens and samples should be handled withcare. Defects in the samples should be characteristic of theprocess being tested and not due to handling of the specimens.6.3 Equipment Selection and Use6.3.1 Bar code verifiers can consist of various pieces ofequipment with differing capabilities and
21、 features. Usersshould select a device that meets the operational, application,and specification requirements of their application. Particularattention should be paid to what application or industrystandard(s) the device must measure against and that theoptical input device be matched to the type of
22、 materials to betested.6.3.2 The aperture size and wavelength has a significantimpact as to the grade results obtained. The ANSI GuidelineX3.1821995 R recommends the aperture diameter based onthe “X” dimension of the bar code being verified. The apertureand wavelength specified in industry applicati
23、on standardstakes precedence over the ANSI guideline, even if some “X”dimension ranges do not agree with the ANSI recommenda-tions. If measuring aperture diameter is not specified, selectaperture diameter based upon the ANSI ANS X3.1821995 Rrecommendations shown below.Diameter 9X9 Dimension (in 0.00
24、10 in.) Range0.0030 in. 0.0040 to 0.007 in.0.0050 in. 0.0071 to 0.013 in.0.0100 in. 0.0131 to 0.025 in.0.0200 in. 0.0251 in. and larger6.3.3 The equipment selected should be set-up, pro-grammed, if necessary, and calibrated to the manufacturersrecommendations.NOTE 2This is extremely important as imp
25、roper use of verificationequipment through incorrect set-up, or calibration, or both, can causemisleading results.6.3.4 Care should be taken in the selection of the locationwhere verification is performed. The operator should be awareof unusual ambient light conditions that may affect readings.Addit
26、ionally, calibration of the device should be performedunder the same ambient lighting conditions as those where thetesting will be performed. The infinite pad method referencedin ANSI ANS X3.1821995 R should be used to preventoptical affects caused by the opacity of the sample substrate. Inthe absen
27、ce of materials for the infinite pad method, an opaqueblack matte surface can be used under the test sample toprovide a worse case optical situation.6.3.5 Bar code symbols should be scanned in both direc-tions (left to right and right to left) and over numerous areas ofthe symbol. This practice will
28、 ensure a better overall indicationof the bar code symbols total quality.6.3.6 Operator proficiency can influence the results. Opera-tors must be trained and care should be taken in all testingsituations. It is recommended that statistical methods beemployed to reduce the effects of operator variabi
29、lity and thatoperators undergo periodic retraining. As a quality measure-ment function, bar code verification should be approached thesame as any other quality control or quality monitoringfunction.6.3.7 ANSI ANS X3.1821995 R specifies ten scans of asymbol are required to obtain a symbol grade. The
30、number ofsymbol grades or scans taken from a particular test sampleshould be based upon statistical methodology to ensure theresults meet the necessary levels of confidence required. Pleaserefer to MIL-STD 105D for guidance on sampling levels andtechniques.7. Report7.1 A Scan Reflectance Profile (SR
31、P) is a record of thereflectance values (0 % to 100 %) measured along a single lineacross the entire width of the bar code. These values arecharted to create an analog representation of the bar code. Thescan reflectance profile grading method identifies relativelevels of print quality. Each SRP will
32、 be graded as A, B, C, D,or F (Scan Grade) for one or possibly more of specified criteria.The grading scheme follows academic letter grades A, B, C, D,and F where A is the best grade and F the lowest. After creatingthe SRP, a count of the elements (bars and spaces) determinesif the bar code conforms
33、 to some type of symbology, but beforethis can be accomplished, edge determination must be done.7.1.1 Edge DeterminationA Global Threshold is estab-lished halfway between the highest reflectance value and thelowest reflectance value seen in the profile. Edge determinationis done by counting the numb
34、er of crossings at the GlobalThreshold confirming whether the count conforms to or is6As an adjunct to the ANSI standard, the Uniform Code Council and AIM USA,created a unique set of primary and secondary Bar Code Calibration Standards inconjunction with Applied Image, Inc. These bar code standards
35、are calibrated toANSI Methodology and traceable to NIST. Though verifier manufacturers also mayhave NIST traceable calibration/correlation standards available, the sole source ofsupply of these test standards known to the committee at this time is Applied Image,Inc., 1653 East Main Street, Rochester
36、 NY 14609. If you are aware of alternativesuppliers, please provide this information to ASTM Headquarters. Your commentswill receive careful consideration at a meeting of the responsible technicalcommittee, which you may attend.F 1851 98 (2003)2considered nonconforming to a legitimate bar code symbo
37、logy.If the bar code conforms it PASSES (Grade A); if it isconsidered nonconforming it FAILS (Grade F). The formula isas follows:GT = Rmin+ SC/2,Rmin= Reflectance Min, andSC = Symbol Contrast.7.1.2 DecodeA bar code will PASS on Decode when theestablished bar and space widths can be converted into th
38、ecorrect series of valid characters using the Reference Decodealgorithm for a given symbology and or application and isgraded Pass (A) or Fail (F).7.1.3 Minimum Reflectance (Rmin)The reflectance valuefor at least one bar must be half or less than the highestreflectance value for a space and is grade
39、d Pass (A) or Fail (F).The formula is as follows:Rmin# .5 Rmax= PASS, Rmin.5Rmax= FAILwhere:Rmin= Reflectance min, andRmax= Reflectance max.7.1.4 Minimum Edge Contrast (ECmin)Each transitionfrom a bar to a space, or back again, is an “edge” whosecontrast is determined as the difference between peak
40、values inthat space and that bar. The edge that has the minimum contrastfrom the transition from space reflectance to bar reflectance, orfrom bar to space, is the Minimum Edge Contrast or ECminandis graded Pass (A) or Fail (F). The formula is as follows:ECmin= Rsmin Rbmax(worst pair)where:Rs = Space
41、 Reflectance, andRb = Bar Reflectance.7.1.5 Symbol Contrast (SC)Symbol contrast is the differ-ence between the highest reflectance value and the lowestreflectance value in the scan profile and is graded A, B, C, D,or F. The quantitative criteria for the symbol contrast grades aregiven in ANSI ANS X3
42、.1821995 R. The formula is asfollows:SC=RmaxRminwhere:SC = Symbol Contrast,Rmax= Reflectance Max, andRmin= Reflectance Min.7.1.6 Modulation (MOD)Modulation has to do with howa scanner sees wide elements (bars or spaces) in relationship tonarrow elements, as represented by reflectance values in thesc
43、an profile. Scanners usually see spaces narrower than bars,and scanners typically see narrow spaces being even lessintense or not as reflective as wide spaces and is graded A, B,C, D, or F. The quantitative criteria for the modulation gradesare given in ANSI ANS X3.1821995 R. The formula is asfollow
44、s:ECmin/SCwhere:ECmin= Edge Contrast Min, andSC = Symbol Contrast.7.1.7 DefectsDefects are voids found in bars or spotsfound in the spaces and quiet zones of the code. Voids, spots,smudges, and other defects in bar code symbols can yield poorscanning results, and thus, will yield lower verification
45、results.Each element is evaluated individually for its reflectancenonuniformity. Element reflectance nonuniformity is the dif-ference between the highest reflectance value and the lowestreflectance value found within a given element and is graded A,B, C, D, or F. The quantitative criteria for the de
46、fect grades aregiven in ANSI ANS X3.1821995 R. The formula is asfollows:ERNmax/SCwhere:ERNmax= Element Reflectance Nonuniformity, andSC = Symbol Contrast.7.1.8 DecodabilityDecodability is the measure of theaccuracy of the printed bar code against the appropriatereference decode algorithm. Each symbo
47、logy has publisheddimensions for element widths and provide margins or toler-ances for errors in the printing and reading process. Decod-ability measures the amount of margin left for the readingprocess after printing the bar code. Different decodabilitycalculation methods are used for each type of
48、symbology beingtested. The decodability calculations are programmed into theverifiers, and decodability is graded A, B, C, D, or F accordingto the quantitative criteria for the decodability grades given inANSI ANS X3.1821995 R or in supplemental industrystandards.7.1.9 Overall Profile GradeThe lowes
49、t grade received byany of the following parameters; edge determination decode,minimum reflectance, symbol contrast, modulation, decodeand decodability.7.2 Scan GradeThe lowest grade received for any qualityparameter in a scan reflectance profile. For example, if a gradeof A or PASS is received for all quality parameters except forModulation, which received a grade of C, the overall ScanGrade is C. Ten SRP Scan Grades are recommended todetermine the symbol grade. The reason for averaging tenscans is purely for vertical redundancy. Quality
